Flexible cords below non-plenum raised floors (not an article 645 space)

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kanaka360

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Long time reader, first time poster here.

As I understand article 400, flexible cords are not allowed below raised floors unless article 645 is used. I have found various threads here indicating that flexible cords may be allowed below raised floors, so long as the raised floor is not a plenum space. Can someone point me in the right direction as far as where the code indicates that this would be allowed in a non-plenum space? Is this only allowed for article 645 applications?

This article appears to also indicate that this would be allowed in a non-plenum space.
http://www.mikeholt.com/mojonewsarchive/NEC-HTML/HTML/Cords-and-Fixture-Wires~20031229.htm

Since it doesn't specifically say "raised" floor in 400.8(2), and because it's not a concealed space, I suppose the argument could be that it doesn't specifically say you can't, but it also doesn't specifically say you can, which makes me wary....

Thoughts? If there is a code section that I'm missing that specifically talks about the non-plenum raised floors, please point me in the right direction.

Thanks!
 

iwire

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Maybe I am missing something but this seems very clear to me.


400.8 Uses Not Permitted. Unless specifically permitted in 400.7, flexible cords and cables shall not be used for the following:


(5) Where concealed by walls, floors, or ceilings or located above suspended or dropped ceilings
 

GoldDigger

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... and because it's not a concealed space, I suppose the argument could be that it doesn't specifically say you can't, but it also doesn't specifically say you can, which makes me wary....

Thoughts? If there is a code section that I'm missing that specifically talks about the non-plenum raised floors, please point me in the right direction.

Thanks!
If the floor is a metal grate, I suppose you could argue that the space under it was not concealed.
But if you have to lift a tile for access, that would be concealed to me.
In either case it would not be inaccessible, but that is not what the provision cares about.
 
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kanaka360

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Location
Boise,ID
Right, I agree with you both, but there is certainly a notion out there that if it is not a plenum, flexible cords below a raised floor are acceptable. The link from the original post says:

"You can put cords within a raised floor not used for environmental air, because
this is not concealed space (see Article 100 for the definition for
"exposed")."

As I mentioned, I've also seen this in a few other threads around here, just wondering where this is coming from.
 

kanaka360

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Boise,ID
It does make sense to me that an accessible floor is not considered "concealed". You can lift up a floor tile just as easily as you can open an access panel in the wall.
 

GoldDigger

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If the floor is a metal grate, I suppose you could argue that the space under it was not concealed.
But if you have to lift a tile for access, that would be concealed to me.
In either case it would not be inaccessible, but that is not what the provision cares about.

Second take: That was using the common speech definition of concealed. The NEC use of the word is, of course, far more specific, and on that basis I agree that a raised floor is neither structural nor part of the building finish.
The area above a suspended ceiling would not be concealed either, but there are provisions that refer specifically to suspended ceilings and do not rely on the word concealed.

2011:
Concealed. Rendered inaccessible by the structure or finish of the building. ....

The space inside a stud wall is concealed because the sheetrock, although not structural is part of the finish of the building. Not so for the tile type of raised floor.
 

kanaka360

Member
Location
Boise,ID
400.8 Uses Not Permitted. Unless specifically permitted in 400.7, flexible cords and cables shall not be used for the following:

(5) Where concealed by walls, floors, or ceilings or located above suspended or dropped ceilings

I would argue that they are not concealed by floors, given that the definition of "concealed" is "rendered inaccessible". A raised floor is certainly accessible. Note that for ceilings, both ceilings and suspended ceilings are specifically listed. I feel that if the intent of the code was not to allow cords below raised floors, it would specifically say floors and located below raised floors. Regardless of what the intent is, I'm not willing to stake my reputation on being able to argue this one with the AHJ, so we'll probably avoid it. I really was just looking for any additional clarification that might be in the code, but it doesn't sound like there is any.
 

kanaka360

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Location
Boise,ID
Thanks GoldDigger. I didn't see your post until I had replied, but I think that makes it fairly clear to me. We're going to end up putting the outlets in floor boxes anyway, but at least I learned something today!
 

iwire

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Thanks GoldDigger. I didn't see your post until I had replied, but I think that makes it fairly clear to me. We're going to end up putting the outlets in floor boxes anyway, but at least I learned something today!

The NEC is far from perfect, there are inconsistencies. It is written by a number of panels, but when we read this

(5) Where concealed by walls, floors, or ceilings or located above suspended or dropped ceilings

I think that considering they directly mention concealed by suspended ceilings it is impossible to turn around and say a lift out floor tile is not concealing the cords.

The intent is to keep cords visibable.

I don't think you find more than a few AHJs that would allow cords under a raised floor that was also not a 645 application.
 

Gregg Harris

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Electrical,HVAC, Technical Trainer
The NEC is far from perfect, there are inconsistencies. It is written by a number of panels, but when we read this



I think that considering they directly mention concealed by suspended ceilings it is impossible to turn around and say a lift out floor tile is not concealing the cords.

The intent is to keep cords visibable.

I don't think you find more than a few AHJs that would allow cords under a raised floor that was also not a 645 application.

I would agree, both locations are identical in nature and to keep the cords visible is the intent.
 

GoldDigger

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I think that considering they directly mention concealed by suspended ceilings it is impossible to turn around and say a lift out floor tile is not concealing the cords.

Take a close look at the code language again. It says nothing about being concealed by suspended ceilings.
It lists prohibited uses where the wire is concealed and then adds another prohibited use where the wire is simply located above suspended ceilings.

To me this argues that they do not consider the space above a suspended ceiling to be concealed within the code definition, but they want to prohibit that use anyway. Whereas for the space under raised floors, which is also not concealed, they choose not to add a specific prohibition.

I originally thought of concealed as hidden from sight, as you argue, but that is not the definition of concealed explicitly adopted by the code.

However, I also recognize that a good fraction of raised floors, as in computer or other electronic centers, are using that space either as a plenum or "other environmental air space" for supplying cooling air to the equipment enclosures. And in that case, concealed or not concealed does not even enter in.

The trend these days appears to be going in the direction of using dedicated ducts instead of the whole underfloor space, so not all raised floors will be subject to that restriction.
 
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kanaka360

Member
Location
Boise,ID
You're probalby right as far as what most AHJ's would require, they can make interpretations as they like, which is why I said I wouldn't stake my reputation on trying to fight this with an AHJ. The first few times I read 400.8(5), I totally agreed, but after looking into the NEC definition of "concealed", I have to disagree as far as what the code actually says.

I realize the panel putting the NEC together is not made up of english majors, but if the intent is for it to be visible, they're way off, because that's certainly not how it reads now. If you take 400.8(5) for what it actually says, the question is, are cords "rendered inaccessible" by raised floors? No way.
 
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